In the pumping of liquid, there are sometimes situations in which a volume of air is drawn into the intake of the pump. One example, without limitations, is found in fire trucks which pump liquid from various sources, such as for example, a lake, a tanker truck, a hydrant and a tank. Such air volume or slug is often introduced into the pump after uncoupling the pump inlet from one fluid source and connecting said inlet to a different fluid source. Another introduction of an air slug into the pumping system sometimes results from the suction of the pump being undesirably near the surface of liquid where a vortex might form and draw air into the pump with the liquid.
Irrespective of how the volume of air or gasses enter the system, their occurrence during pumping operation causes an undesirable pressure drop down stream of the pump and a corresponding increase in engine speed and pumping speed owing to the reduced engine load. Once the slug of gas has passed the pump, liquid will enter the pump which is then operating in an over-speed condition. This will cause an undesirable and sometimes dangerous pressure surge downstream of the pump and will also function to shorten the life of the pump and engine.
A situation for which this pumping system is particularly adapted and useful is on a fire truck wherein detrimental discharge pressure surges sometimes causes firemen to be unable to control the discharge hose which will whip around and injure or kill.
The present invention is directed to overcome one or more of the heretofore problems, as set forth above.